Superconductivity was discovered in complex oxides in the late 1980s. Of the many materials discovered, only two have advanced technologically such that they have the potential for commercial applications: Bi2Sr2CaCu2Ox (also termed BSCCO, or Bi2212) and YBa2Cu3Oy (or YBCO). Of these two, only Bi2212 is capable of performing in the form of a round wire, which gives it a distinct advantage for applications requiring high-current cables, such as the magnets needed for high energy physics (e.g., for particle colliders such as the Large Hadron Collider), fusion reactors, and high magnetic field solenoids, including those utilized in nuclear magnetic resonance (NMR) spectrometry and imaging. By contrast, YBCO can be formed into wide, thin tapes but not round wires. Moreover, Bi2212 is the only high-field superconductor that does not have anisotropic properties, which is another advantage over YBCO.
Bi2212 superconductors for magnets are typically manufactured in the form of multi-filament composite wires. The composite has a silver alloy matrix that contains the oxide superconductor in the form of a large number (500-1000) of small (about 15 micrometers in diameter) filaments. Development of wires of this form has progressed with some success. Progress in development of Bi2212 wires, however, has recently stalled due to significant challenges that to date have not yet been overcome. First, to date all Bi2212 wires have been manufactured using oxide Bi2212 powders that have already been reacted to form the Bi2212 superconducting phase. The formation of the wire, however, requires that the composite be drawn from an initially large billet into the final wire form (the final wire may be, for example, about 1 mm in diameter or less). Silver alloys have been the only option for use as the sheathing material for a variety of reasons, but silver alloys are soft whereas the Bi2212 powders are hard. Consequently, during wire drawing the filaments do not densify, and in the final product about 30% of the filament space is actually voids. These voids significantly reduce that ability of the wire to carry electrical current, and also make the wire relatively fragile. Second, there are very few manufacturers of high quality Bi2212 starting powders, and the wire performance depends greatly on the quality of the powders. The lack of availability of starting powder limits the amount of research and development that can move forward, and scale-up for the production of large quantities of wire is an uncertain challenge.
In view of the foregoing, there is a need for providing improved methods for forming superconducting materials such as Bi2212, and for forming wires and other articles based on such superconducting materials.